Water tanks and other types of containers for holding liquids often must be monitored to ensure that a proper liquid level is maintained. If the liquid level rises too much, the tank or other container may overflow. Alternatively, if liquid level drops too low, the tank can run dry. Accordingly, it may be desirable to employ a pump to add liquid if the level drops too low or to remove liquid if the level becomes too high. Various types of audio and visual warning circuits may also be employed to report that a liquid level in a container is not within desired parameters.
Traditionally, in water pumping stations, mercury switches have been used to activate and deactivate a pump so that water level in a storage tank is controlled. Recently, however, the danger of mercury contamination and environmental damage has prompted a move to eliminate and replace these switches. As a result, the use of single station horizontal and vertical reed switches have become increasingly popular. Typically, these devices employ permanent magnets to operate a reed switch. More particularly, the reed switch is mounted in a permanent fixture and the magnet is mounted on either a cylindrical float (the vertical switch) or a pivoting float (the horizontal switch). Unfortunately, in many water storage tanks lime, slurry, grease or other contaminants tend to build up and interfere with the operation of the float. As a result, the switch may be rendered inoperable.